**5. Conclusion**

This study carried out a LCA assessment on 1 kg of OPC so as to analyze the environmental impact of cement production using both the midpoint (processoriented) and endpoint (damage-oriented) approaches. The production process modeled after the rest of the world excluding China, India, Europe, US and Switzerland; therefore, dataset modeled after the world was used to carry out the assessment. This dataset was extracted from Ecoinvent database incorporated in the SimaPro 9.0.49 software was used for this study.

In the midpoint assessment, characterization result showed the impact of 18 impact categories. The top three with highest impacts: global warming (0.911 kg CO2 eq), terrestrial ecotoxicity (0.438 kg 1,4-DCB), and fossil resources scarcity (0.0784 kg oil eq) were further analyzed. Global Warming has the highest environmental impact of 0.911 kg CO2 eq. Global warming is often times a result of high GHG emission and its effect is seen in changes in climatic conditions. Further analysis on this impact category shows 88.5 kg out of 0.911 kg CO2 eq is the actual CO2 gas emitted and 75.6 kg out of 88.5 kg of CO2 was emitted from the clinker production phase. This shows that clinker production is the production phase that contributes the most to global warming. In the analysis of terrestrial ecotoxicity, result showed that numerous heavy metals that that are emitter into the air are great contributors to this impact category; few of these metals with high values are copper (61.5%), Mercury (11%), zinc (7.77%), nickel (7.53%), vanadium (7.06%). These metals are emitted at the raw material extraction, energy generation and transportation production phases. Fossil resource scarcity shows that the most used resources are coal, crude oil and natural gas and they are maximally used at the energy generation production stage.

In the endpoint assessment, characterization result showed the impact of 22 impact categories. These impacts were further classified into three damage categories based on area of significance to life (AoSL): human health, ecosystem and resources with values of 1.22E<sup>6</sup> DALY, 3.1E<sup>9</sup> species/yr. and 0.0231 USD2013 respectively. Disability-adjusted life years (DALY) represents the years of life spent or years of life damaged because of environmental impacts. Species/yr. denotes the species lost within a year in water bodies and the environment as a whole; USD2013 represent the currency used for the monetary value of economic loss leading to increase in prices as a result of continuous extraction of resources. Analysis of the damage to human health category showed that 67.3% of the damage to human health is as a result of emission of CO2 while the rest are from NOx, so2 ch4, particulates mater <2.5 μm and water; 70.1% of these emissions was from clinker production stage while the rest was for energy generation and transportation. The same trend was observed in the analysis of damage to ecosystem; 79.9% of the damage to ecosystem was found to be as a result of co2 emission while the rest are from NOx, SO2 CH4, methane and water; 77.8% of these emissions was from clinker production stage while the rest was for energy generation and transportation. This thereby establishes the fact that whatever will affect human health will equally affect ecosystem. As also seen in the midpoint emission, clinker production is the production phase has the highest contribution to impact consequently causing damage and CO2 is the most significant pollutant. The analysis of resources shows that the resources that are maximally used are from the energy generation production phase and they are: crude oil (67.9%), natural gas (16%), hard coal (11.4%) and clay (4.19%). This shows that petroleum is the main fossil fuel used for the production of OPC.

The outcome reveals that emission from clinker production contributed immensely to global warming and consequently damage to human health and ecosystem. This study concludes that production processes with impact hotspots are clinker production and energy generation (fossil fuel and electricity) and the major pollutant is CO2 gas emission. The result of this study is in line with other similar studies (including those that do not implement the 2 approaches) carried out but there is variation in the result of the resources because of variation in the fossil fuel sources used for energy generation. Finally, it is recommended that using alternative fuels in place of fossil fuels can be a means to reduce the pressure on fossil resources. Incorporation of best available techniques (BAT) in cement production process, partial replacement of clinker constituent with pozzolans like fly ash are other strategies to reducing impact of cement production. Also, CO2 gas emitted can be trapped, stored and used as input for industrial processes which will reduce global warming impact. Further study is the sensitivity analysis of environmental impacts of cement when alternative fuel and materials are used.

## **Acknowledgements**

The authors gratefully acknowledge Durban university of technology for an enabling environment. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

## **Conflict of interest**

Authors declare that there is no conflict of interest with respect to the study.

*Life Cycle Assessment of Ordinary Portland Cement (OPC) Using both Problem… DOI: http://dx.doi.org/10.5772/intechopen.98398*
